On the toolbar (when you have the graph activated), choose Plot Area from the drop-down box. Then drag the corners of that box. You can also select the edges of it and move the entire plot area as you wish.
You can also select this by clicking near the piechart itself, but I often have difficulty selecting the plot area on pie charts, so I prefer the toolbar method for that particular type of chart and selection.
Depending on where your legend is, it still may move it or change it. If that happens, simply select the legend and move it to where you want. Same with the datapoint labels, if that's what you're actually talking about.
